[Modernman]

A private company cannot dictate to people what they do after business hours, only during the time the people are working and getting paid.

The company is not forcing anyone to give up smoking. If you want to keep smoking, you are free to quit.

They might as well tell their workers what clothes to wear, what car they can drive and what music they can listen too.

Employers can impose such rules, and they do. With regards to clothes, employees have been fired for posing in Playboy. With regards to cars, I know of an environmental NGO in DC whose employees are forbidden from owning certain types of cars, such as SUV's.

Your employer can pass a lot of BS rules that affect your personal life. Don't like them? Quit.

[longtermmemmory]

SUV at work perhaps. SUV at home, would not stand any legal challenge.